Interesting Chain Tension System & Retro-Direct

I saw this at CicloSDias in San Diego last weekend.
The bicycle is currently set up as a single speed, and to provide adequate chain tension, an additional chainring is placed in the drive train.

The owner previously had the bicycle set up as a retro-direct, using two gears on the rear wheel and two chainrings on the crank. He said the elevated chainstays made it ideal.

Here is a video of the bicycle in action as a retrodirect-